Neuropeptides are an abundant and diverse set of neuronal and endocrine transmitters responsible for modulating vital functions of the nervous system such as learning and memory, food intake, and energy balance. Despite their importance, there is currently no way to systematically assay neuropeptide function in vivo. This project aims to create and validate a genetic resource for comprehensively studying the functional impact of secretion of all neuropeptides. Such a tool will allow for the study of physiological and behavioral impact of specific neuropeptides in a way that has not previously been possible. In C. elegans, there are 115 pro-neuropeptide genes that encode over 250 distinct neuropeptides (1). In preliminary studies we have found that a stretch-sensitive neuron, the DVA, secretes both endogenous and ectopically expressed neuropeptides in response to muscle contraction induced by the acetylcholinesterase inhibitor aldicarb. This peptide secretion has assayable effect on cholinergic and GABAergic transmission at the neuromuscular junction. We propose two specific aims that are designed to exploit the inducible and rapid release of neuropeptides from DVA. We will express the entire library of C. elegans neuropeptide genes in the DVA neuron and confirm their inducible secretion to create a resource to assay for neuropeptide function in vivo. Because neuropeptides have such diverse physiological effects, this genetic resource will be useful to a broad community of researchers interested in investigating the impact of neuropeptide secretion on such processes as lifespan, metabolism, chemotaxis, egg-laying, and synaptic transmission. We will then demonstrate the impact of this tool by utilizing it to screen for neuropeptides that regulate synaptic function at the neuromuscular junction with behavioral and electrophysiological approaches. This will create a research pipeline for comprehensive study of how neuropeptides regulate synaptic efficacy and produce adaptive changes in behavior. )